I have been looking in to doing some test driven development for one of the applications that I\'m currently writing(OLE wrapper for an OLE object). The only problem is tha
Microsoft won't allow 3rd party extensions for the express editions for visual studio. As Jon Limjap already mentioned Testdriven.Net won't work for visual studio. Other test-runners that integrate with visual studio like the one in resharper won't work either.
Luckilly most unit-testing frameworks like Xunit.Net, Nunit and MBUnit have their own stand-alone testrunner. You can compile your tests with visual studio express then load the test-assemblies in the testrunner and execute the tests.
You can't test code in web-projects this way. You need to put the tests and the code you want to test in separate class-libraries. Web projects are compiled on demand by the webserver and this makes testing difficult.
A useful addition by Marc Gravell: Web site projects are compiled on demand. Web application projects are pre-compiled.
So you should be able to run tests in a web-application project with an external test-runner.